Earth's Structure and Plate Tectonics
The Earth's structure consists of several layers, each with unique characteristics. Understanding tectonic hazards in geography Edexcel B requires knowledge of these layers and their properties.
Vocabulary: Lithosphere - The solid outer layer of the Earth, comprising the crust and uppermost mantle.
The layers of the Earth, from outermost to innermost, are:
- Crust (0-100km thick)
- Mantle (liquid/solid, 900-1600°C)
- Outer core (liquid, 4000-5000°C)
- Inner core (solid, 5400°C)
Convection currents in the mantle, generated by heat from radioactive decay in the core, drive plate tectonics. This process involves:
- Heating of the fluid asthenosphere
- Rising of less dense hot liquid
- Cooling and sinking of denser material
- Continuous cycle pushing and pulling plates
Highlight: Convection currents bbc Bitesize Geography explains this process in detail for students.
The three main types of plate boundaries are:
- Divergent (plates move apart)
- Convergent (plates collide)
- Conservative (plates slide past each other)
Definition: Plate boundaries bbc Bitesize defines these as areas where tectonic plates meet and interact.